Exercise 20 Page 202

Consider the given equation of a line. y= 1/2x-5 To find the slope perpendicular to this line, we need to find the negative reciprocal of 12.

m_1 * m_2 = -1

Substitute

m_1= 1/2

1/2 * m_2 = -1

MoveRightFacToNumOne

1/b* a = a/b

m_2/2=-1

MultEqn

LHS * 2=RHS* 2

m_2 = -2

We have found that -2 is the negative reciprocal of 12. Using this information we can write a general equation in point-slope form for the lines perpendicular to the given line. y- y_1 = -2(x- x_1) Since we know that point P( 4, 0) should be contained in the perpendicular line, we can substitute it for ( x_1, y_1). By doing so, we will be able to write the equation of the line perpendicular to the given one, and containing point P. y- 0 = -2(x- 4) ⇕ y=-2(x-4)